If you are having trouble with your Dometic or Norcold rv refrigerator
then you are at the right website. We specialize in rebuilding the ammonia
cooling units that power the rv refrigerator. The cooling unit is the set of
metal coils that are attached to the back of your refrigerator. The three
most common signs that indicate a bad cooling unit are:

A strong ammonia smell inside the
box, this would indicate a leak in the evaporator section. Look at
our link rebuilding process for a more detailed understanding of how we
repair a cooling unit with an evaporator leak. If the unit has
leaked for an extended amount of time the ammonia smell may no longer be
present but you will probably hear a gurgling sound coming from the back
of your refrigerator a few minutes after you turn it on.

If the controls are working and the
cooling unit is heating up in the back but there is no cooling taking
place inside the box this could be a sign of a blockage in the boiler
section.

Another thing to look for, if you unit is not cooling but you don't
smell ammonia inside the box, look for a yellow powder around or just
above the burner located at the back of the unit. This would indicate a
leak in the boiler section. Since this leak is outside the box you would
rarely smell it inside. I see these boiler leaks more frequently in the
newer Norcold and Dometic cooling units.

The three example above should help you identify your cooling unit
problem. If you feel you have a different problem with your refrigerator or
need further advice on troubleshooting your problem, call me at the above
number or read below for a better explanation of what an ammonia absorption
cooling unit requires to operate properly.

What a Cooling Unit Needs to Operate Properly

The cooling unit, or coils, of an ammonia absorption
refrigerator is the heart of the refrigerator--it does the actual cooling.
Everything else on the refrigerator either supports the cooling unit, or is
an accessory. No matter how simple or complicated the controls of the
refrigerator are, all cooling units require the same three things to
operate:

The unit has to be level

The unit has to have adequate ventilation

The unit has to have CORRECT heat

A fourth issue is raised if the cooling unit has recently
been changed. The cooling unit has to have been properly installed into
the refrigerator.

If the three above requirements are provided to the cooling
unit, it should work and should work well. If it doesn't work well, then it
is a bad cooling unit. It's really that simple. (Also, failure to meet the
three requirements above when the refrigerator is in operation can cause
permanent damage to the cooling unit.) Of course, don't overlook mitigating
circumstances such as a main door that seals very poorly, which would cause
a good cooling unit to look bad because of warm air continuously entering
the box.

Also, if the cooling unit seems to work poorly only during
warm weather, it's possible that one of the requirements above is in a
border line state. In other words, the venting, for example, may be adequate
for mild weather, but not adequate for warm weather. A cooling unit could
also be border line, but it would be prudent to look elsewhere first.

Testing the Cooling Unit

First of all, if the cooling unit cools properly on one heat
source (i.e. gas or electric) and not the other, then the cooling unit, with
only a few exceptions, is good and the problem lies in the heat source that
is not functioning properly.

Secondly, there are obvious signs of a bad cooling unit.

If you smell ammonia in or around the refrigerator, and
you haven't recently used ammonia for cleaning, the cooling unit is bad.
No further testing is necessary.

If sodium chromate is present on the outside of the
cooling unit, the cooling unit is bad. Sodium chromate is a
yellowish-greenish powder in solution inside the cooling unit. If sodium
chromate is outside the cooling unit, the cooling unit has a hole in it.

If you hear a relatively loud gurgling or percolating
sound when the refrigerator is in operation (being heated), it is a sign
of a bad cooling unit. The key words here are "relatively loud". A good
cooling unit percolates when in operation, and if you get close enough and
listen carefully enough, you can hear it percolate. However, if you hear
noise a few feet away, it is a sign that the cooling unit has lost
pressure and is bad.

Testing the cooling unit is simply insuring that the three
necessary requirements for the operation of a cooling unit (level,
ventilation, correct heat) are met. Do whatever it takes to meet these
requirements. If you suspect a venting problem, pull the refrigerator and
set it on the floor. In fact, pulling the refrigerator and setting it on a
level floor meets two of the requirements and leaves only one, correct heat,
to worry about. Always test the refrigerator on the electric heat source,
unless you are unable to because you have a gas only refrigerator. The
reason for testing on the electric side is if the electric heat element gets
hot, you can be better than 95% sure that you have correct heat, whereas
even a poor gas flame will produce heat. To insure that the heat element is
getting hot, you can touch the insulation pack (a rectangular or round sheet
metal container filled with insulation located directly above the propane
burner) to see if it is warm after about a half hour of operation. CAUTION:
touch the pack lightly at first; it is possible under certain conditions for
the pack to get super hot and burn you. If the insulation pack does not get
warm, you have an electrical problem that needs to be corrected before
continuing. If an electrical problem is not the electric heat element itself
and/or you want to insure that some other electrical component (such as a
thermostat) is not interrupting the heat element, you can hot wire the heat
element for better testing conditions. The only weak link in this testing
procedure is the less than 5% of the time that a working heat element is not
producing the correct heat. See hot wiring for information on verifying the
output of the heat element.

After you have provided the cooling unit with its three
requirements, allow plenty of time for the cooling unit to function. You
should see signs of cooling in the freezer after about two hours. Allow six
to eight hours, or even over night, for an empty refrigerator to come down
to temperature. The ammonia absorption style of refrigeration is slower than
the compressor style in terms of initially bringing the refrigerator down to
temperature. However, once the desired temperature is reached, there should
be no problem in maintaining that temperature.

If you have done everything in this section up to this point
and the cooling unit does not work or does not work well, the cooling unit
is bad and will need to be rebuilt or replaced.